"He set it up like a rental place, with pictures of the family," Sgt. Denny Wood of the Pierce County Sheriff’s Department said, according to the News-Tribune. "I think it was staged so when CPS (Child Protective Services) came, it would look like a loving family."

Police say that Powell rented it in 2011 but neighbors said they never saw anyone there. When Powell learned he could not keep his children, he rigged the house, turning it into a bomb, authorities have said. On Feb. 5, when his sons, Charlie, 7, and Braden, 5, came to visit, he slammed the door in a social worker’s face, slashed the boys with a hatchet and lit a match to a can of gasoline.

The house exploded within moments, killing all three. The social worker was uninjured.

Powell had been in the media spotlight because he was the only person of interest in his wife’s disappearance. In December 2009, Susan Powell, 28, went missing in Utah, where the family lived. At the time, Powell told police that she had run away from their family during a midnight camping trip.

On Monday, Wood detailed what police believe occurred on that fateful Sunday: "The little boys come in. He takes them to the back and hits them with the hatchet. Josh Powell scatters gas. He walks around the house, tossing it on the walls and floor. He puts the five-gallon gas can by the front door. He sits with the other can between his knees."

Josh Powell took the lives of his two sons in a house fire. Powell was a 'person of interest' in his wife's 2009 disappearance. NBC's Miguel Almaguer reports.